Supporting construction for the stator of a ring generator of a wind turbine

ABSTRACT

The present invention concerns a wind power installation having a support structure for the stator of a ring generator, wherein the support structure has a plurality of support arms. The object of the present invention is to reduce the sound emissions emanating from a wind power installation as set forth in the classifying portion of the claim. A wind power installation having a generator, preferably a ring generator, comprising a rotor and a stator which has a mounting means for stator windings, wherein the stator is held by a support structure which has a plurality of support arms and wherein an odd number of support arms are provided and/or the support arms are irregularly spaced.

TECHNICAL FIELD

[0001] The present invention concerns a wind power installation having asupport structure for the stator of a ring generator, wherein thesupport structure has a plurality of support arms.

BACKGROUND OF THE INVENTION

[0002] Wind power installations have long been known and are producedand marketed for example by Enercon under the type designations E-40,E-58 or E-56.

[0003] Operation of such wind power installations always involves theproduction of sound emissions which can be perceived to be disturbing,at least in the area relatively closely around the wind powerinstallation.

SUMMARY OF THE INVENTION

[0004] Therefore the object of the present invention is to reduce thesound emissions emanating from a wind power installation as set forth inthe classifying portion of the claim.

[0005] That object is attained by a wind power installation having thefeatures recited in claim 1. Advantageous developments are described inthe appendant claim.

[0006] While in the case of a support structure with an even number ofsupport arms which can develop given frequencies uniformly in theperipheral direction of the ring generator, which are then perceived assound waves that are experienced as being a disturbance, such soundemissions are entirely suppressed or reduced when the structure involvesan odd number of support arms and/or irregular spacing of the supportarms.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The invention will be described in greater detail with referenceto the drawings in which:

[0008]FIG. 1 shows a simplified view of the state of the art,

[0009]FIG. 2 shows an alternative configuration of the state of the art,

[0010]FIG. 3 shows an embodiment of a support structure according to theinvention, and

[0011]FIG. 4 shows an alternative view of the conditions of theembodiment according to the invention as shown in FIG. 3.

DETAILED DESCRIPTION OF THE INVENTION

[0012]FIG. 1 shows a support structure having six radially extendingsupport arms 12, the outer portions of which are arranged at an equalspacing relative to each other. The stator 10 of a ring generator isfixed to those outer portions. The stator 10 is indicated in FIG. 1 bybroken lines.

[0013] With this design configuration of a support structure,oscillations 20 can be formed distributed over the periphery between thesupport arms 12. The uniform spacing between the support arms 12 and thewavelength of the oscillations 20, which respectively coincidestherewith, can give rise to an effect which is referred to as the ‘drumeffect’. What is more crucial in terms of sound emission however are theformation of natural modes (natural forms) which can be produced uponexcitation with a given oscillation. Those natural modes are usuallydependent on or determined by the geometry of the overall object.

[0014]FIG. 2 is an alternative view showing the situation in the case ofthe known support structure. In FIG. 2, the oscillations 20 are shown inconjunction over the periphery of the support structure with the supportarms 12. The oscillations are shown by a dotted line displaced by half aperiod, and identified by reference numeral 20 a.

[0015] If any point on the periphery of the support structure (or amolecule of air at that location) is considered, it will be seen thatthere, depending on the respective phase position of the oscillations20, 20 a, the position thereof alters along a line indicated by thearrow 30. Therefore for that point here there is a bidirectionaloscillation, as in the case of an eardrum.

[0016]FIG. 2 shows three complete periods of an oscillation, distributedover the periphery of the arrangement, so that three respective in-phasepoints are always oscillating with the same magnitude and in the samedirection. Those oscillations result in a regular ‘pump movement’ in thestator of the generator, which is perceived as sound.

[0017]FIG. 3 shows in simplified form a support structure according tothe invention. It has an odd number of support arms 12 (in this caseseven). It will be appreciated that the object of the present inventioncan also be attained with five support arms. In a preferred embodiment,at least seven support arms 12 are used for reasons of the requiredstrength of the support structure. In FIG. 3, the stator 10 of the ringgenerator is again indicated by broken lines.

[0018]FIG. 4, similarly to FIG. 2, shows a representation of theoscillations which are linked together over the periphery of the supportstructure. In this case, once again a sequence of oscillation events isidentified by reference numeral 20 while reference numeral 20 a alsorepresents those oscillation events but displaced by half a period withrespect to the oscillations identified by reference numeral 20.

[0019] The oscillations identified by reference numeral 20 show threecomplete oscillation periods in the portions 21, 22 and 23 while onlyhalf a period occurs in the portion 24.

[0020] By virtue of that oscillation pattern, two positive half-waves(half-periods) are directly mutually adjacent, more specifically at thebeginning of the portion 21 and in the portion 24, so that accordinglythe drum effect cannot occur at least at that location and is thus atleast reduced in its overall effect.

[0021] If a mechanical construction such as for example the supportstructure of a generator produces an unwanted sound emission, that canusually be explained on the basis that, under the action ofoscillations, the entire support structure produces so-called resonancesor also ‘natural modes’ (natural forms). Those ‘natural modes’ arefirstly dependent on the geometry of the entire object, in additionthere is also a certain frequency dependency of various natural modes.

[0022] With the design configuration according to the invention of thesupport arms of the status, the frequency pattern of that component issuch that frequencies at which in particular sound-emitting naturalmodes (natural forms) could occur are avoided as much as possible.

1. A wind power installation having a generator, preferably a ringgenerator, comprising a rotor and a stator which has a mounting meansfor stator windings, wherein the stator is held by a support structurewhich has a plurality of support arms and wherein an odd number ofsupport arms (12) are provided and/or the support arms are at least inpart irregularly spaced.
 2. A wind power installation according to claim1 characterised in that the support structure for the stator has sevensupport arms.
 3. A wind power installation having a generator,preferably a ring generator, comprising a rotor and a stator which has amounting means for the stator windings, wherein the stator is held by asupport structure, wherein the support structure is so designed that itproduces substantially no or only slight sound-emitting natural modes(natural forms) in the normal operating range.